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Full text of "The manufacture and properties of iron and steel"

FUEL.                                                 163
of any save true gaseous components, but in the products of a soft-coal fire there are certain amounts of soot and tar. Some of these are deposited in the conduits, but they do not constitute a great part of the total energy. In the case of an. exposed 7-foot iron pipe, 250 feet long, the condensation of tar amounted to only three-tenths of 1 per cent, of the total heat value,* while the gas itself, after passing through, the tube, contained a proportion that represented from one-tenth, to one-eighth of the total heating power. In spite of the low calorific power of this tar it is found that, when the suspended matters are removed by scrubbing, the value of the gas is reduced very seriously, for the tar gives luminosity to the fiame and thereby renders it able to heat not only by direct impact, but by the no less potent action of radiation. It is by virtue of this quality that the luminous flames from the dense hydrocarbons surpass the clear products of an anthracite fire.
The investigation given in Sec. VHIi showed that the losses of energy in a producer as operated at Steelton were as follows:
Lost as carbon in ash.....................................   2.1
Sensible heat of dry gas.................................13.7
Sensible heat of steam in gas............................   0.7
Radiation and conduction (by difference) ..............   5.1
Total..................................................21.6
The total shows that over one-fifth of all the heat value of the coal is lost. The. figure for radiation and conduction is determined by difference, and hence bears all the errors in the determinations. The other items offer ground for discussion.
(1) The carbon in the ash.
In Sec. Vllli reference was made to experiments by von Jiiptner in which the loss of carbon in the producer ash represented 20 per cent, of the total value of the coal, for the ash from the producer contained 74 per cent, of carbon and only 26 per cent, of true ash. Such a waste is entirely unnecessary, for it is possible to run soft-coal gas producers where the ash contains less than 20 per cent, of carbon, and averages from 12 to 18 per cent. It is possible to estimate very closely how much is lost if we know the percentage of carbon in the ash and the percentage of ash in the original coal. The latter point must be taken into consideration, for if the coal
* The Open-Hearth Process.   Trans. A. I. M. E., Vol. XXII., p. 376.